A PDF can have an open password that protects access to its contents, or a permissions password that asks compatible readers to restrict actions such as printing. The latter is not a strong substitute for encryption. Choose a strong, unique open password and use a tool that supports modern encryption.
Save a protected copy and test it in another reader before deleting or sending anything. Share the password through a different channel from the file. Consider whether the filename, email subject, or document metadata reveals sensitive information even when the pages are encrypted. For highly sensitive files, also control who receives them and how long copies remain available.
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